Key: Detainees 'electing to be on Christmas Island'

John Key has defended his stance over the detention centre on Christmas Island.

He says while he doesn't agree with Australia's policy of sending people to the island, detained Kiwis can leave the centre at any time and return to New Zealand.

"We don't like this policy, the whole way through we've said we don’t like New Zealanders being sent there," Mr Key told the Paul Henry programme this morning.

"We don’t like what's happening, but my point is simply this: if you are someone being sent to Christmas Island you don't need to go there. You can come back to New Zealand and you can come back either within a few days if you have no issues, or potentially a few weeks. So people are electing to stay there. They can come back and we'll facilitate that."

But Labour leader Andrew Little says he has been advised it could take as long as 20 days for detainees to come to New Zealand, something Mr Key says is "absolute nonsense."

"It's a couple of weeks.

"I actually have a responsibility to New Zealanders who they are coming home to, to make sure that they are safe – and that means I have to put protection around these people, essentially, and make sure there's supervision around them."

Yesterday the Prime Minister was accused of being "gutless" by Labour MP Kelvin Davis for not helping detainees on the island.

Mr Key replied to his comments in Parliament, saying, "It's not actually easy because some of [the detainees] are rapists, some of them are child molesters, and some of them are murderers and these are the people the Labour Party are saying are more important to support than New Zealanders who deserve protecting when they come back here."

The prisoners are known as '501s', after section 501, the law that forces them out of Australia because of previous criminal convictions.